They were training locals when the police station they were using as a base was surrounded by 80 armed men.

The “Red Caps” had just 50 bullets each, dodgy radios and unroadworthy vehicles. We understand Col X believes British spies knew that an Iranian-inspired attack was imminent but troops on the ground were not warned.

Lawyers for the Red Caps’ families believe his intelligence will support their claim that the murders were preventable.

The families still believe the full story of how their loved ones died has not been told and they want a fresh inquest.

Col X was in charge of an SAS intelligence-gathering team sent in days after the massacre. He later contacted the dead soldiers’ lawyers when he learned they were calling for a fresh inquiry.

He added: “The Ministry of Defence, supported by the Attorney General’s Office, has made it clear Lt Col X can provide a statement of what he knows.

“The Army appears to have a view which is at odds with this.

“They have no lawful basis for adopting the stance they have, it is misconceived and contrary to the interests of justice.”

An MOD spokesman said: “Our thoughts remain with the families of those killed in this tragic incident.

“The MOD is aware of claims that a former soldier has sensitive new information relevant to this case, but despite our repeated request this has not been made available to us, and it remains to be seen whether it exists.

“We remain committed to keeping the families informed of any progress in this case.”